Apparatus for Collecting a Representative Fluid Sample

ABSTRACT

An apparatus for collecting a fluid sample from a reservoir contains a sample gathering chamber, a motor driven hydraulic pump, a motor mechanically coupled to the hydraulic pump, an electronic controller for influencing the actions of the motor, and a power source for running the motor. A piston which is sealably and movably disposed may be located within a tubular portion defining the sample gathering chamber. The apparatus may also further contain a metering component for regulating pressure.

TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to equipment utilized in conjunctionwith operations performed in relation to subterranean wells and, inparticular, to a sampler for collecting and recovering a representativefluid sample from a subterranean formation of interest.

BACKGROUND OF THE INVENTION

Without limiting the scope of the present invention, its background willbe described in relation to exploratory subterranean well operations, asan example.

As used herein, the words “comprise”, “have”, “include”, and allgrammatical variations thereof are each intended to have an open,non-limiting meaning that does not exclude additional elements, steps,or embodiments. Furthermore, it should be understood that as usedherein, “first”, “second”, “third”, etc. are arbitrarily assigned andare merely intended to differentiate between two or more elements,devices, embodiments, etc., as the case may be, and does not indicated aspecific sequence, nor should be viewed as a limiting sequence.Furthermore, it is to be understood that the mere use of the term“first” does not automatically imply that it should be followed by a“second” or for that matter a “second by a “third”.

As used herein, the phrases “hydraulically coupled,” “hydraulicallyconnected,” “in hydraulic communication,” “fluidly coupled,” “fluidlyconnected,” and “in fluid communication” refer to a form of coupling,continuum, connection, or communication related to fluids, and thecorresponding transmission of flows or pressures associated with thesefluids. In some embodiments, a hydraulic coupling, connection, orcommunication between two components describes components that areassociated in such a way that fluid pressure may be equally transmittedbetween or among the components. Reference to a fluid coupling,connection, or communication between two components describes componentsthat are associated in such a way that a fluid can easily flow betweenor among the components. Hydraulically coupled, connected, orcommunicating components may include certain arrangements where fluiddoes not flow between the components, but fluid pressure may nonethelessbe transmitted across an interface such as a diaphragm or piston.

As used herein, a “fluid” is a substance having a continuous phase thattends to flow and to confirm to the boundaries of the vessel containingit. A fluid can display the properties of a liquid or a gas, dependingon where, based on its composition, temperature and pressure, it fallson the gas-liquid continuum.

From simple beginnings, the search for oil reserves has moved into moreremote locations and more technically demanding reservoirs andenvironments. Exploratory wells are often drilled with the goal offinding new hydrocarbon reserves, identifying the nature of thereserves, and then verifying their economic viability. Consequently,after a well has been drilled and underground hydrocarbon bearing stratahave been identified, it is desirable to determine the physicalcharacteristics of the strata in question and also the chemicalcharacteristics of the hydrocarbon in place. The physicalcharacteristics provide invaluable clues as to the extent of thereservoir and how fast it can be made to produce its hydrocarboncontent. The chemical characteristics are invaluable in defining themonetary value of the hydrocarbon reserves as also the best mechanism bywhich the recovered reserves can be handled and further processed. Boththe physical and chemical characteristics are invaluable pieces ofinformation for defining the monetary value that can be assigned to aprospective discovery.

Numerous pieces of equipment and methodologies are available and wellknown to those active in the industry for determining the physicalproperties of a reservoir. These include the extensive suite of toolsavailable during Measurement while Drilling (MWD) operations, LoggingWhile Drilling (LWD) operation, Wireline Formation Testing (WFT)operations, Production Logging (PL) operation, and Surface Well Testing(SWT) operations, including methodologies such as pressure drawdowntesting, gamma-ray logging, neutron density logging, MRI logging, etc.For the sake of brevity these will not be further discussed, though anabsence to do so should not be viewed as a limitation to thisdisclosure.

A detailed understanding of the reservoir fluid including its chemicaldescription may be viewed as perhaps the most significant aspect of anywell test operation. A sample of the reservoir fluid is invaluable forundertaking a detailed laboratory PVT analysis, where the initials PVTstand for Pressure, Volume, and Temperature. A representative reservoirsample is also crucial for generating a detailed chemical analysis ofthe hydrocarbon phase. For these and many other reasons it should bereadily apparent to those familiar with the oil industry that collectingand recovering a representative sample of reservoir fluid is a crucialfirst step in defining the economic viability of a newly discoveredhydrocarbon reservoir.

There are a number of opportunities during the exploratory andproduction cycle when a reservoir sample can be collected. Recenttechnological developments have made it possible for hydrocarbon samplesto be collected as early as the drilling phase. During drillingoperations samples can be collected in samplers associated with thedrill string. After the conclusion of the drilling phase and while thedrilled borehole is still an open hole, namely exposed formation rock,samples can be collected during traditional Wireline Formation Testing(WFT) operations. During WFT a number of tools directed at delivering abetter understanding of the physical and chemical nature of thereservoir are introduced into the borehole via wireline. Included inthis tool string is a set of samplers for collecting bottomhole samples.

Once casing is set and the openhole is cemented, a Drill Stem Test orDST can be undertaken. During a DST operation samples can be collectedon pipe or tubing by incorporating carriers specifically designed forcarrying a multiplicity of samplers from the surface to the subterraneanzone of interest on the work string. A cased hole environment alsoaffords numerous opportunities to run a set of production logging toolson e-line or wireline. and offers another excellent opportunity tocollect samples of the reservoir fluids. Stand alone slickline or e-linesampling is also feasible in a cased hole environment.

The sample collecting process itself is complicated and requires anumber of distinct and necessary steps. First a subterranean zone ofinterest needs to be identified that would warrant the expense ofundertaking a sampling operation. Next some means needs to be identifiedfor locating a sampler adjoining to or in the vicinity of the zone ininterest. With the sampler at location some mechanism is needed totrigger the sampler to collect a sample at the correct instance duringsome specific static or flow period appropriate to the testing beingundertaken of the subterranean zone of interest. Once the sampler istriggered the sample should be collected in a controlled fashion so asto minimize the possibility of the sample flashing two phase. Once thesample collection has been completed, the sample has to be locked inplace in the sampler, and simultaneously a high pressure charge of gas,usually nitrogen, is released against the sample to exert pressure onthe sample and keep it single phase during recovery to the surface. Atthe surface the sample is usually transferred, again at high temperatureand pressure, into long term storage bottles.

Recognizing the need to preserve the sample single phase and at somehigh pressure after collection, it should be obvious that equalprecautions need to be taken during the collection of the sample.Consequently, all samplers designed to collect a single phase sample arealso designed to collect the sample at a pressure that is as close aspossible to the pressure of the reservoir where the fluid to be sampledresides. Furthermore, as most samples are collected ahead of a movingpiston located in a tubular section, preserving the integrity of thesample during the collection phase requires that the movement of thepiston be slowed down to prevent the sample from flashing two phase theinstant the sampler's tubular section is exposed to the high pressurefluid phase to be sampled.

Slowing the movement of the sample collecting piston is most easilyaccomplished by the simple expediency of incorporating somenon-interacting fluid, usually referred to as a displacement fluid, onthe backside of the sampling piston, namely the side opposite to wherethe sample will collect. As a consequence, as the sample enters thetubular section on one side of the sample piston causing it to belaterally displaced, this lateral movement of the piston will result ina corresponding lateral movement of the displacement fluid. If thelateral movement of the displacement fluid is further constrained byforcing it through a very fine constriction or choke, then the resultingvery slow movement of the sampling piston due to the restriction of themovement of the displacement fluid is successful in delivering a singlephase sample at reservoir pressure, where flashing has been minimized oreven eliminated.

Furthermore, it should be readily obvious to one familiar with the artthat the very presence of the displacement fluid will require that thesampler be equipped with some low pressure dump chamber into which thedisplacement fluid can be ejected while the sample is being collected,and where the displacement fluid will stay stored during the entiresample collection, recovery to the surface, and subsequent storage untilsuch time that the sample is transferred out of the sampler for furtheranalysis. It is significant that once the displacement fluid movesthrough the choke or metering section and into the dump chamber, it hascompleted its function and is now redundant.

A sample that is successfully captured downhole is subject tosignificant thermal gradients during subsequent recovery to the surface.Invariably a sample is collected at some temperature higher than, andusually much higher than ambient. During recovery to the surface itfollows that the temperature of the sample must decrease until itreaches equilibrium with the ambient temperature. This temperature dropduring the recovery step causes the sample to shrink in volume, and ifthe volume of the container with sample in it does not change, thisshrinkage of the sample causes the sample pressure to drop. If thesample pressure should approach, or fall below the saturation pressure,the sample will go two phase with gas breaking out, or even multi phasewith gas and solid breaking out, at which point the sample is no longerconsidered representative. Depending on the particular circumstance,when the sample goes multi-phase, considerable effort and expense willneed to be expended to return it to a representative monophasic state.

In order to mitigate the detrimental effects of shrinkage it has provennecessary in the past that a collected sample be immediately brought incontact with a high pressure nitrogen charge in order to bring thesample pressure up to some desirable value adequate for the sample tostay single phase during recovery to the surface and subsequenttransportation and storage. Consequently, each sampler must be connectedto a high pressure nitrogen source, to which end each sampler can haveits own nitrogen source, which is by far the more prevalent design, or,as is seen in some very unique cases, there can be a common nitrogensource for more than one, or even all the samplers. Irrespective of theexact design, it is imperative that the pressure and volume of thenitrogen source be such that it will successfully maintain the samplepressure at least 2000 psi above and preferably even higher than thepressure at which the sample was collected, and maintain this highpressure during the entire subsequent history of the sample.

To reiterate, a successful sampling operation requires some receptaclerated for high pressure and temperature service and equipped with aplurality of associated chambers and mechanisms such that when saidreceptacle is brought alongside a subterranean formation of interest andtriggered or activated, it will allow the fluid contained in thesubterranean formation of interest to enter and gather in theappropriate chamber associated with the receptacle. Furthermore, theentry of the said reservoir fluid into the said chamber is deliberatelycontrolled by the slow drainage of a displacement fluid from a chamberadjoining the chamber receiving the sample into some immediately orclosely associated chamber specifically included for the purpose ofreceiving the displacement fluid. The controlled movement of thedisplacement fluid is most effectively implemented by forcing thedisplacement fluid to flow through a restrictive choke as it transitionsbetween the two afore mentioned chambers. Once the sample has beencollected it is necessary that the sample be locked in place to trap itso it is contained for further transportation and handling.Simultaneously, a source of high pressure gas, preferably nitrogen,contained in a chamber either adjoining the sample chamber or in closeproximity to the sample chamber, is brought in indirect communicationwith the collected sample so as to take the pressure of the sample to atleast 2000 psi above the pressure at which it was collected and keep itat this high pressure during the subsequent recovery to the surface.

All of this requires a number of intricate parts that must work inprecise unison if the sampling step is to be successful. Consequently,it should be obvious to one well versed in the sampling art that thereis a need for a sampler of simpler design that is easier and safer tooperate and would deliver a more reliable performance than is presentlyavailable.

SUMMARY OF THE INVENTION

The present invention disclosed herein is directed to a samplingapparatus for collecting and preserving a representative sample of asubterranean reservoir fluid. Additionally, the proposed design has theflexibility and versatility to function effectively in numeroussubterranean environments and applications including open hole and casedhole situations. Furthermore, the proposed design has the flexibilityand versatility to function effectively when conveyed to thesubterranean formation of interest by any of a number of means. Themeans of conveyance may include slickline, wireline, e-line, coiledtubing, pipe, tubing, etc. The proposed design also has the flexibilityto deliver a representative sample irrespective of the fluid orhydrocarbon type encountered.

Additionally, the proposed design is unique in that it eliminates theneed for a high pressure nitrogen source resulting in a much simpler,safer, and more compact device. Furthermore, the uniqueness of thedesign delivers samplers with much higher recovery pressures relative tothe more conventional design using a nitrogen charge.

To achieve the above stated objectives the method of the presentinvention will incorporate an appropriately sized electrical motor intothe body of the sampler. The power needed to run the electrical motorwill come from either an adjoining battery pack or an attachedelectrical cable if the sampling operation is being undertaken usingwireline or e-line. The electrical motor in turn will drive a hydraulicpump, either directly or through the agency of a set of gears, with theresulting output of the hydraulic pump being a pressurized hydraulicfluid. The pressurized hydraulic fluid in turn can be brought to bear onthe non-sample side of sample collecting piston to exert pressure on thesample collecting piston, and subsequently pressure on the sampleitself. By this simple expediency the need for the cumbersome anddangerous nitrogen source is eliminated. Furthermore, the very nature ofthe mechanism being exploited is guaranteed to deliver a higher and morereliable recovery pressure than would be delivered by the existingnitrogen source.

Associated with the electric motor and in electrical communication withwould be control electronics such as processor devices, data storagedevices, and communication devices, or alternatively, a centralizedcontrol unit may be provided that communicates with and controls one ormore of the individual components that comprise the aforementionedsampler. The purpose of the control electronics is to provideinstructions to the electrical motor to define exactly how and when themotor is to function. For example, with programmable controlelectronics, instructions provided either as input at the surface andstored in memory associated with the control electronics before start ofsampling operations, or transmitted during sampling operations eithervia an optical cable, or an electrical cable, or as an acoustic signalfrom the surface to an appropriate receiver in or in the vicinity of thecontrol electronic, would provide instructions on the direction, speedand duration that the electrical motor should run in order to providesome necessary function associated with the sampling process.

In operation, the sampler would be positioned at the subterraneanformation of interest via one of the methods of conveyances mentionedabove. When so positioned the sampler is in the start position with thesample collecting piston at the far end of the tubular section that thesample will collect in. In this configuration there is minimal availablevolume in the space ahead of the piston where the sample will collect,while the space behind the piston is completely occupied by a workingfluid. Depending on the method of conveyance, it might be necessary toinstruct the programmable controller while still at the surface toundertake a specific set of actions in a specific time sequence startingafter some preset and predetermined period of time. For example, justbefore the sampler is attached to the method of conveyance, a starttimer may be set with a time delay of say, and as an example only, tenhours. Accordingly, when ten hours have transpired the sampler operationwill be initiated, starting with a set of actions needed to begincollecting a sample.

As part of this start operation some passageway between the tubularelement of the sampler where the sample will collect, and the fluid tobe sampled present in the external surroundings of the sampler, will beopened so that sample is now free to flow into the sampler. However,sample movement into the sampler will be restricted by the presence ofthe aforementioned working fluid positioned behind the sampling piston,which working fluid must be moved out of the tubular element before thesample piston can move and sample can enter the tubular element. Themovement of the working fluid is further restricted by requiring it toflow through a metering section, as a consequence of which the entiresample collection step is appropriately slowed down. This retardation ofthe sampling process is crucial to allowing the collected sample to stayin pressure equilibrium with the surrounding fluid being sampled.Pressure equilibration minimizes the possibility of the sample flashingtwo phase during collection and thus being compromised.

It is extremely significant that even though the working fluid appearsat this stage in the sampling process to be no more functional than thepreviously cited displacement fluid, the two are unique in their action.Thus, once the traditional displacement fluid has completed itsrestrictive action and been displaced into some retaining space, it isrendered useless. Quite to the contrary, for this application, as willbe shown below, the working fluid first serves to restrict the rate ofthe sample collection step, but then will be reversed in its role, andthrough the action of the hydraulic pump serve to maintain pressure onthe collected sample. This is a unique and distinguishing feature ofthis design relative to the samplers that have preceded it.

Because of this duality of purpose, the working fluid can be consideredto traverse two distinct spaces. In the first instance, the workingfluid occupies the space behind the sampling piston and upstream of themetering section. From the instant sampling commences downhole to suchtime that sampler returns to the surface and all the sample istransferred out of the sampler, the pressure of the working fluid inthis space will be at least the pressure of the collected sample, andusually higher. This can be considered the high pressure space for theworking fluid. But once the working fluid passes through the meteringsection and enters the low pressure side, it is stored prior to use forthe required pressure maintenance at a much lower pressure, and this canbe considered the low pressure side of the working fluid.

This movement of the sample piston and associated sample collectionactivity will continue until the piston has traversed a specifieddistance, or separately and/or concurrently, a specified volume ofworking fluid has moved from behind the sample collection piston or highpressure space to the adjoining chamber or low pressure space assignedfor the collection of the working fluid. At this point further movementof the sample collection piston is curtailed and the sample isconsidered to have been collected.

With the sample appropriately positioned in the sample chamber, theelectric motor, and by association the hydraulic pump, are nowactivated. The electric motor working in conjunction with the hydraulicpump will act to move working fluid from the low pressure space to thehigh pressure space, which in turn will serve to generate theover-pressure required to compress and preserve the sample single phaseduring the ensuing recovery step associated with returning the singlephase sample to the surface. Additionally, this excess pressuregenerated by the hydraulic pump will cause the pressure of the collectedsample to exceed the external pressure, or the original pressure atwhich it was collected, and this differential pressure can be used toactivate any of a number of mechanisms that will effectively lock thesample in place.

Without in any way limiting the scope of this invention, a simplemechanism whereby the sample would be locked in place as the hydraulicpump overpressures the working fluid on the back side of the samplepiston would call for the use of a simple check valve. The check valvecould be positioned between the sample entry section and the space aheadof the sampling piston, and so aligned that once the trigger mechanismis activated so that sample collection can commence, fluid flow can onlygo from outside the sampler into the sampler. Once the sample collectionstep is completed and the electric motor activates the hydraulic pump toincrease the pressure of the working fluid in excess of the surroundingfluid, this excess pressure will serve to close the check valve andprevent loss of the sample. A condition that will persist as long as thepressure of the sample exceeds that of the fluid surrounding thesampler. This is only meant to be an exemplary embodiment and not alimiting embodiment, as any similar approach that will use theoverpressure or some other such means to lock in the sample will sufficefor this purpose.

With the sample locked in place, continued movement of the sample pistondue to continued action of the electric motor in conjunction with thehydraulic pump can be used to pressurize the sample to any desired valueabove its collected value such that its single phase recovery isassured. The desired single phase recovery pressure can be set at thesurface and monitored during the time the sample is being collected byvirtue of pressure sensors set in the sample side face of the samplepiston, or even on the working fluid side, and which can be used tocontinuously monitor the pressure of the collected sample.

The present invention disclosed herein is directed to a samplingapparatus for collecting and preserving a representative sample of asubterranean reservoir fluid. Additionally, the proposed design has theflexibility and versatility to function effectively in numeroussubterranean environments and applications including open hole and casedhole situations. The present design is also very effective for thecapture of all types of hydrocarbon systems ranging from highly viscouslow API oils to very compressible gases. Furthermore, the proposeddesign has the flexibility and versatility to function effectively whenconveyed to the subterranean formation of interest by any of a number ofmeans. The means of conveyance may include slickline, wireline, coiledtubing, pipe, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more thorough understanding of the components, features andadvantages of the present invention, reference is now made to thedetailed description of the invention along with the accompanyingfigures in which corresponding numerals in the different figures referto corresponding parts and in which:

FIG. 1 is a cross sectional schematic illustration of a novel samplerdesigned to facilitate the capture and recovery of a representativesample of fluid from a subterranean formation for further handling andanalysis.

FIG. 2 is a non-limiting, exemplary cross-sectional schematicillustration of a specific component of a novel sampler. Details of ametering component and a check valve component are presented.

FIGS. 3A and 3B are non-limiting, exemplary cross-sectional schematicillustrations of specific components of a novel sampler.

FIG. 4 is a non-limiting exemplary cross-sectional schematicillustration of a novel sampler in accordance with an exemplaryembodiment of the present disclosure.

FIG. 5 is a non-limiting exemplary cross-sectional schematicillustration of a novel sampler in accordance with an exemplaryembodiment of the present disclosure.

While embodiments of this disclosure have been depicted and describedand are defined by reference to exemplary embodiments of the disclosure,such references do not imply a limitation on the disclosure, and no suchlimitation is to be inferred. The subject matter disclosed is capable ofconsiderable modification, alteration, and equivalents in form andfunction, as will occur to those skilled in the pertinent art and havingthe benefit of this disclosure. Obvious variations on these exemplaryembodiments will be readily apparent to others well versed in the artand are hereby incorporated into this disclosure by virtue of theirobviousness. The depicted and described embodiments of this disclosureare examples only, and not exhaustive of the scope of the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The making and using of various embodiments of the present invention arediscussed in some detail below. However, it should be appreciated thatthe present invention provides many applicable and synergisticinnovative opportunities which can be embodied in a wide variety ofspecific contexts. The specific embodiments discussed herein are merelyillustrative of specific ways to make and use the invention, and do notdelimit the scope of the present invention. Consequently, the followingembodiments are presented only to facilitate a better understanding ofthe proposed invention, embodiments of which might be applicable tovertical, horizontal, deviated or otherwise nonlinear wellbores in anytype of subterranean formation. These embodiments may be applicable toexploratory wells, test wells, production wells, or injection wells.

Referring initially to FIG. 1, therein is depicted a novel sampler withthe designation 100, operable to collect and retain a representativefluid sample from a subterranean zone of interest. The subterranean zoneof interest can be considered to be a repository of some fluid type,which could be a hydrocarbon species in the form of oil or gas, ormixtures of the two, or even water, or mixtures of hydrocarbon oil, gasand water. Without in any way limiting the scope of the invention, thephases most often encountered during well testing in oil fieldsituations could be solids of both organic and inorganic nature, anaqueous phase, hydrocarbon liquid, and hydrocarbon gas. As a rule, useis made of accessories such as tubing, piping, wireline, slickline,valves, sensors, samplers etc. to access a subterranean zone of interestso that its properties can be evaluated. Part of this evaluation stepincludes positioning a sampler or a plurality of samplers alongside asingle or multiphase mixture that represents a reservoir fluid that isdesired to be collected. When sampler and fluid to be sampled areproperly positioned with reference to each other, some internal pre-setor external stimulus or signal is provided to activate the sampler andstart the sampling process.

A sampler usually comprises a tubular section in which the desiredsample accumulates, and additional tubular sections that help to achievethe sampler's objectives. Even though the tubular section is circular inform, there is no reason why it could not be oval, or square, or evenrectangular, other than the fact that the circular tubular sections areeasiest to machine, fabricate and manipulate. For convenience, andwithout in any way limiting the scope of this invention, the tubularsection will be considered to be circular.

The first tubular section, identified as 121 is the section into whichthe sample of interest will flow by lateral movement of the samplepiston 120 from left to the right as viewed in the plane of the page. Aneffective hydraulic seal is present between the piston 120 and thetubular section 121 to eliminate cross contamination of the sample beingcollected to the left of the piston and the working fluid to the rightof it, and is achieved through the use of elastomer seals 111, a set ofwhich are portrayed. Movement of the piston will move working fluid 130from tubular section 121 through passage 160 and into tubular section181.

With continued reference to FIG. 1, the front or leading piece asdefined by viewing the sampler from left to right and identified in thefigure as 101, acts as the required trigger which responds either to apre-set or to some subsequent external or internal stimulus or signal sothat the sample collection process can be initiated. The actual triggercan take many forms, be differently positioned, and have numerous meansof activation, so that the offered generic description is merely anexample of a first step needed to start the sampling process and is notmeant in any way to limit the scope of this disclosure.

In a non-limiting embodiment, the trigger could be a simple on-off valvewhich can rotate from a closed position to an open position, thusallowing the surrounding fluid to enter the tubular section 121. In anon-limiting embodiment the rotation of the valve can be facilitated byan electric motor which gets the power to turn the valve via aself-contained battery pack together with a timer set to close a switchand deliver the electric power after some prearranged time has elapsed.Or, again without imposing any limitations, the switch to deliver thepower can be activated by some external signal such as a pressure pulse,or an acoustic signal, or an electro-magnetic signal, or even an opticalsignal conveyed via an optical cable.

In yet another non-limiting embodiment, the trigger could be a simplemechanical, spring loaded device activated by a spring loaded clock setat the surface, such that after a set pre-arranged period of time hasexpired the clock returns to its start position and trips the trigger tothe on position. There are any numbers of such triggers commerciallyavailable and in wide use and they will not be discussed in furtherdetail herein. Suffice it to say that some trigger mechanism will beactivated at the appropriate time to initiate the start of the samplingactivity by allowing the fluid surrounding the sampler to enter thesampler.

Once the trigger has been activated, the fluid to be sampled can nowfreely enter the openings in the sampler identified as 110 and startfilling the sampler. These openings can also take many forms and bevariously located without in any way limiting the scope of thisdisclosure. For example, even though the openings are portrayed alongthe circumference of tubular element 121, the opening could as easily besingular and in front of the sampler indicated by the trigger component101. Suffice it to say that there is either a singular or multiple setof openings in the sampler, usually at the leading edge, which connectvia some passage to a point just in front of the sample collectingpiston identified as 120, such that when the sampler is triggered tostart collecting a sample, the fluid to be sampled and which is usuallysurrounding or in communication with the sampler, is brought in contactwith the space in front of piston 120, i.e. between the sample piston120 and the sampler openings 110 so that sample collection can commence.

The element identified as 140 is a distinct spacer that providesdemarcation between the tubular sections 121 and 181 while alsocontaining other functional elements as discussed in some detail below,all of which are needed to deliver the proper and complete samplingfunction. The end piece marked as 191 is usually some generic connectorthat allows the sampler to either be attached to some other sampler asin a sequence of samplers, or to a larger carrier that is carrying anumber of samplers, or to some other means of conveyance of the sampler,either slickline, wireline, coiled tubing, or electrically poweredtractor motor, needed to convey the sampler to the subterraneanlocation.

As the fluid to be sampled enters the sampler it first encounters thesample piston identified as 120. In order to minimize the possibilityfor flashing the sample and making it go two or more phases, the samplepiston 120 is backed up by the working fluid 130. The working fluid 130can be any convenient fluid whose restricted movement through a meteringsection, shown as 160, slows the movement of the sample piston and doesnot allow the sample to flash. In this instance it is significant thatthe working fluid is also a dielectric fluid, in the sense that it willonly poorly conduct electricity.

Another advantage of immersing all the components in a dielectricworking fluid would be the heat sink such a fluid would represent.Essentially, because of the high temperature environment the motor andelectronics will be exposed to, in addition to the heat the motor andelectronics will generate when called upon to perform their functions,it might be advantageous to improve the heat transfer characteristics ofthe environment surrounding the motor. This can be most convenientlyachieved by immersing the motor and its ancillary electronics in amedium that is electronically non-conducting, most conveniently adielectric fluid. Because the surrounding fluid is electricallynon-conducting, the working of the motor will in no way be affected.This is a relatively routine practice for downhole tools and will not bediscussed in greater detail here. Suffice it to say that the performanceand longevity of the motor and the accompanying battery can beconsiderably enhanced by improving their ability to dissipate heat, astep most easily accomplished by immersing the motor, battery andassociated electronics in a dielectric fluid. A typical non-limitingexample of such a working dielectric fluid would be say the Paratherm NFheat transfer fluid available from the Paratherm Corporation.

The metering section is invariably a choke or some similar restrictionthat limits the rate at which the working fluid can move through it.Without in any way limiting the scope of the invention, the meteringsection as discussed in this particular embodiment could be bestrepresented by a Lee Visco Jet type device as available through the Leecompany, Connecticut, USA. The Lee Visco Jet device is commerciallyavailable and descriptions of the detailed workings are present in theopen literature, for which reason it will not be discussed in greatdetail herein. Let it suffice that a mechanism for restricting the flowof the working fluid 130 between the tubular sections 121 and 181 isavailable such that the controlled collection of a sample representativeof the fluid surrounding the sample entry point 110 is feasible.

The metering section 160 is firmly encased and hydraulically sealed inthe fixed element 140, usually in advance of or in association with apassage shown as the tubular element marked 145. The passage marked as145 serves to provide an outlet for the working fluid 130 to transitfrom the left side of fixed element 141 to the right side in a slow andcontrolled fashion as the working fluid transits through the meteringsection. A non-limiting embodiment of this metering device and passage145 are presented in greater detail in FIG. 2.

Adjoining the metering section 160 is a check-valve component marked as161 which serves to provide a unidirectional restriction to the flow ofworking fluid. For the purpose of this embodiment the unidirectionalflow would be from tubular 181 to tubular 121. Flow in the oppositedirection, namely from tubular 121 to tubular 181 would be restricted bythe check valve's action. Associated with the check-valve component 161is a tubular element marked 146 so positioned as to allow movement ofpressurized working fluid from the discharge of pump 150 through element146 and into the tubular section 121 and subsequently into the space tothe right of piston 120. A non-limiting embodiment of thisunidirectional check-valve device and accompanying passage 146 are alsopresented in greater detail in FIG. 2.

FIG. 2 presents the metering section 160 in greater detail. A principalelement of the metering section is the Lee Visco Jet unit as discussedabove, and identified as component 202 for controlling the rate of flowof working fluid from tubular section 121 through passage 145 and intotubular section 181. The Lee Visco Jet unit 202 makes a hydraulic sealwith the opening 160 by means of the elastomer seal shown as 201.Consequently, all fluid entering section 160 during the sampling step isforced to go through the metering section. However, once the requiredsample has been collected, the passage through the metering sectionneeds to be closed to curtail further loss of pressurized working fluidthrough the metering section.

This closure is accomplished by the action of the check dart 205 goingon-seat on the sealing surface 215 when closure is required. The seat215 is hydraulically sealed against the top face of the Visco Jet viathe circular elastomer seal 216 so as to ensure that flow of workingfluid is compelled to be past the face of the dart 205 and through theVisco Jet. The seat 215 is held firmly in place by the locking nut 217which screws into the top face of component 160 to hold the entireassembly together, while also activating the seal 216.

The locking nut 217 contains the openings 219, two shown, foraccommodating the shear pins 210, again two shown. During assembly theshear pins are inserted through the openings in the locking nut andpenetrate through to the radial groove 220 cut into the elongatedcylindrical section of the sealing dart. As can be seen in FIG. 2, thepins serve to hold the dart suspended above the sealing face of the seat215 allowing working fluid to flow past the dart and into the meteringsection.

However, once the sample collection step is concluded, the face ofpiston 120 adjoining the side containing the working fluid will beabutted against the face of element 140 containing the meteringcomponent 160. In this configuration the face of piston 120 will exertthe necessary force against the dart 205 to cause the shear pins toshear, thus releasing the dart from its confinement in the openposition. The force of the pressurized working fluid pushing against thereleased dart in conjunction with the spring 211 will now cause the dartto go on seat, essentially shutting of this flow path for the workingfluid. As long as the pressure of the working fluid in the tubularsection 121 exceeds the pressure of the working fluid in the tubular181, the dart will stay on seat and close out that passage.

The component 161, comprises primarily a check dart 265, and serves theopposite function. The check dart 265 is spring loaded via spring 262,while the spring is held in place via the nut 263 which threads into thebody of piece 140. The nut 263 has a passage 264 through it to alloweasy flow of working fluid in either direction through it. The springloaded check dart stays on seat during the entire sample collection stepso that movement of working fluid from tubular section 121 to 181 canonly take place through the metering section 160. However, once thesample collection step is concluded, and the pump 150 is activated tostart pressurizing the working fluid behind piston 120, the highpressure discharge of the pump entering the component 161 via thetubular passageway 146 will force the dart 265 off-seat and allowpressurized working fluid to enter the space behind the piston 120.

Also shown in FIG. 2 is the pressure monitoring device marked 240. Eventhough such devices are quite common in the industry and will not bespecifically discussed in great detail here, the output of such apressure monitoring device plays a significant role in the properoperation of the sampler. In one non-limiting embodiment, the pressuremeasuring device serves to measure and convey the pressure of theworking fluid to the electronic controller associated with the motor,which in turn will control the movement of the electric motor and thepump such that some pre-set value of pressure is maintained during theentire sampling and recovery cycle. Because the working fluid is inhydraulic communication with the collected sample, the pressure measuredat 240 is also the pressure of the collected sample.

In a non-limiting embodiment, the output of the pressure monitoringdevice is shown exiting in the form of two or more leads marked as 230in FIG. 2. This output is inputted into the electronic controller thatserves to define the action of the pump 150. Without in any way limitingthe scope of the invention, consider the case where a sample has beencollected at a reservoir pressure of 6000 psi. In keeping with therequirements of single phase sampling, it would be required that thesample pressure be maintained at least at 6000 psi, and preferably ahigher pressure at least 2000 psi above the reservoir pressure, namely8000 psi during the sample recovery step. By constantly monitoring thepressure and transmitting the reading to the electronic controller, theelectronic controller will in turn activate the pump to deliver therequired pressure and keep the sample single phase.

The choice of pressure at which the sample is maintained as single phaseis case specific, but as a rule should always be at least 2000 psi abovethe pressure at which the sample is collected. Consequently, if a priorknowledge of the reservoir pressure is available, the electroniccontrolling unit can be pre-programmed to keep the collected sample atsome pressure that is at least 2000 psi above this value. On the otherhand, the electronic controller can be set to always keep the pressureat least 2000 psi or higher than the registered sample pressure recordedduring or at the end of the sampling step. This remarkable flexibilityfor pressure maintenance is unique to this design and is anothersignificant distinguishing feature that demarcates this design fromthose that have preceded it.

The pressure transducer needed for this application is quite commonplacein the industry, with any number of variations fit for purpose readilyavailable, so that a lack of elaboration of its exact features andmechanism does not in any way detract from the scope of this invention.As presented in the non-specific embodiment of FIG. 2, the pressureinformation measured by the pressure transducer 240 is conveyed to theelectrical programmable control unit directly by means of the electricalcable identified as 230. However, this should in no way be consideredlimiting, as some other means including but not limited to acoustic orelectro-magnetic means, including a radio or optical signal will beequally effective in conveying the necessary pressure information to theelectronic controller.

Returning again to FIG. 1, element 150 is a high pressure hydraulic pumpwith a set of inlets shown as 151 and an outlet for the high pressuredischarge which is also an extension of the tubular element 146. This isa simple hydraulic pump, and a number of commercial manufacturers can beapproached to deliver a desirable pump for such an application. It isrecognized that a pump specific to such an application will need to becustom designed and manufactured, but this is a relatively routinepractice in the industry. A typical example of a pump applicable forsuch purpose would be a micro-hydraulic pump available from say, andpresented only as a non-limiting example of a potential source, thecompany Petroleum Accessories, Inc., which can be approached to delivera micro-hydraulic pump custom designed for this purpose.

The power required to run the pump 150 comes from the electrical motormarked 153, the drive shaft of which is connected to the drive shaft ofthe pump 150 via the coupling marked as 152. An electric motor ispreferable because they are capable of quickly generating significantamounts of torque which would be needed to work the hydraulic pump 150to generate the significant overpressure that will be required forsingle phase sampling. As presented in FIG. 1, the main shaft of theelectric motor is directly connected at 152 to the drive shaft of thepump, but this need not be the case. Component 153 could be acombination of electric motor and gear box such that the torquedelivered by the drive shaft of the motor can be greatly increasedthrough the working of the gearbox using appropriate gear ratios todeliver the required torque needed to drive the hydraulic pump againstsignificant sample pressure.

The electric motor console identified as 153 can also contain theelectronic controller, not shown separately, that will control theactions of the electric motor. Thus for example, and without in any waylimiting the scope of the invention, certain functionalities can beprogrammed into the electronic controller at the surface, or conveyed bysome additional means from the surface to the electronic controller atthe appropriate time to appropriately influence the workings of themotor. In one non-limiting embodiment, the electric motor and adjoiningpump will stay quiescent until the sample collection step has concluded,at which point the electrical motor and pump will be activated topressure up the working fluid surrounding them and discharge thispressurized fluid through passage 146 into the space to the right ofpiston 120, thus exerting pressure on the collected sample to counterthe pressure drop due to sample shrinkage. As indicated above, theoutput of the pressure monitoring device 240 can also be used toactivate the motor and pump.

In a slickline application, power for the electric motor will come fromthe power pack depicted in FIG. 1 by the number 160 and transmitted tothe electrical motor via the electrical umbilical 154. The power pack inthis instance could be a battery pack, rechargeable or otherwise, withthe capacity to provide the needed electrical energy for the motor toperform its duty over the short number of hours or even days requiredfor a typical slickline sampling operation. In a wireline or e-lineapplication the power pack may be dispensed with altogether and thenecessary power provided by a surface source to the motor via theappropriate electrical conduit. The same electrical conduit can also beused to transmit the necessary instructions required by the electricmotor to perform its sampling function. Understandably, in someapplications it might be appropriate to have a combination of externalpower source and internal battery pack.

In a carrier based application, where a number of such samplers aresimultaneously conveyed to location on pipe or tubing, the power packcould be a much larger separate element carried as part of the carrieritself and used to provide power to a number of samplers. Clearly, andwithout in any way limiting the scope of this invention, the requiredpower source can take numerous forms depending on the specificconveyance mechanism utilized for transporting the sampler to thevicinity of the desired subterranean zone to be sampled.

In slickline or carrier based operations where a battery pack isrequired to deliver the necessary electrical power, the battery pack cantake on any of a number of configurations. In one non-limitingembodiment the power source could be what are routinely referred to asprimary or non-rechargeable cells, a typical non-limiting example ofwhich would be a routine alkaline battery, but could include a host ofvariations such as a lithium air battery, mercury battery, molten saltbattery, zinc based battery, etc.

In yet another non-limiting embodiment, the power source could be whatare routinely referred to as secondary cells or rechargeable batteries,a typical non-limiting example of which would be lead-acid batteries,Lithium based batteries including Lithium-polymer batteries, nickelbased batteries including nickel metal hydride, sodium based batteries,rechargeable alkaline batteries, zinc batteries, etc.

The end piece of the sampler designated by 191 is just an ordinarymechanical connector for attaching a sampler to an adjoining sampler orto any appropriate conveyance mechanism such as slickline, wireline,coiled tubing, pipe, tubing, etc.

The lateral movement of the piston 120 from left to right during thesample collection process will eventually bring the piston in closeproximity or direct contact with the fixed element 140. At this point noadditional sample can be collected and the sampler's function needs torevert to a mode appropriate to the sample's satisfactory recovery tothe surface. Without in any way limiting the scope of this invention,this can be most simply accomplished by a simple on/off switch locatedon the face of element 140 that would abut piston 120 when it reachesthe end of its stroke. Closing off the switch would serve to activate anelectronic programmer, not shown for the sake of simplicity, that wouldinitiate the function of the electric motor and hence the pump, to keepthe sample single phase during recovery to the surface. It should bereadily apparent that neither the action of the switch nor the shearingof the pins 210 can interfere with the performance of each other'sfunction. Thus dimensionally the length of the dart 205 and the verticalposition of the above mentioned switch would be such that the pins 210will shear, following which the switch will activate.

The controlled movement of piston 120 from left to right during thesample collection step due to the slow movement of working fluid out oftubular section 121 and through the metering section 160 will result inworking fluid entering the tubular section 180 through the passageway145. The pump 150, the motor 153, and the battery pack 160 all haveadequately sized passages, shown as 141, between their outside diametersand the inside diameter of tubular 181 such that the working fluidentering at 145 can have access to the complete tubular section 181. Ina non-limiting embodiment, an example of this passage marked 141 isshown in FIGS. 3A and 3B for the pump 150 and the motor 153. One wellversed in the art would have no trouble recognizing that a similarpassageway would also be available for the movement of the working fluidpast the battery pack marked 160. As long as the working fluid is anon-conducting medium there is no issue with completely immersing pump,motor, and battery pack in the working fluid.

Prior to commencement of sampling, the piston marked as 185 in FIG. 1will start adjacent to and abutting the battery pack 160. When samplingcommences, working fluid will enter tubular section 180 and start tofill the dead volume surrounding and adjoining 150, 153, and 160. Oncethe dead volume is filled, continued entry of the working fluid willcause the piston 185 to move laterally from left to right to encompass alarger volume shown as 170. The volume to the right of the piston 185 isinitially charged with some inert gas like nitrogen at some reasonablepressure in the range of 100 to 300 psi. Neither the stated nature ofthe gas nor the initial charge pressure should be viewed as limiting andare meant only to exemplify one embodiment of this invention. Any otherinert gas, for example helium, would work equally well in thisapplication.

The stated initial charge pressure of the gas can also cover a broadrange as dictated by the actual circumstance under which the sampler isto be used. Any judicious initial charge pressure such that when bothpistons 120 and 185 are bottomed out, namely have moved as far right asthey will go, results in the final pressure at 182 being significantlyless than the pressure of the reservoir fluid entering at 110, will beadequate.

The purpose of the nitrogen charge is primarily to exert lateralpressure on piston 185 from right to left such that the tubular section181 to the left of piston 185 is always liquid full irrespective of theangle or configuration of the sampler. Essentially, by virtue of the gaspressure at 182 exerting a lateral force from right to left on piston185, the internal volume of the tubular section 181 to the left ofpiston 185 will always be liquid full irrespective of its configuration,and consequently the pump 150, with its fluid inlets marked as 151, willalways have a full head and be primed for action.

As discussed in a previous embodiment, the hydraulic pump does notactivate until the entire sample has collected in the sampling space,following which, the hydraulic pump acts as a pressure maintenancedevice to assure single phase sampling. In yet another non-limitingembodiment it is feasible to activate the pump during the samplecollection step itself to improve the quality of the collected sample.Thus, for example, even as the sample is being collected and the samplepiston is moving in discrete increments to displace the working fluidfrom space 121 to space 181, the pump, through the agency of theelectrical motor, working under the instructions of the electroniccontroller, can be activated to inject working fluid at high pressurefrom the low pressure side to the high pressure side. In this mode thesample will be repeatedly over-pressured even as it is being collectedto ensure that the sample stays single phase during the collection stepto deliver a better quality sample. Understandably, when the pump stops,the metering action will once again dominate, and sample collection willresume as the working fluid moves through the metering section. Such aunique flexibility in motion is not available with any other samplecollecting tool and makes this design invaluable for a range ofapplications including heavy oils at one extreme and wet condensates atthe other.

Another non-limiting embodiment of this concept is presented in FIG. 4,wherein the flexibility of the design is considerable enhanced byinclusion of a solenoid control valve, marked as 420, in conjunctionwith the hydraulic pump 450. The incorporation of the solenoid controlvalve allows considerably greater flexibility in how the input andoutput to and from the hydraulic pump will be directed. In thisembodiment the electric motor will still drive the hydraulic pump whichwill have a fixed low pressure inlet marked as 418 and a high pressuredischarge marked as 432.

Positioned between the hydraulic pump and the fixed member 140 will bethe solenoid control valve 420 activated by a separate power source 421and controlled by the electronic controller. The solenoid valve assemblywill have a plurality of openings, with 4 shown and marked as 408, 412,416, and 430 for the purpose of this discussion. Internal to thesolenoid valve will be a number of passages and associated pistons,check valves, rotary components, and seals for controlling the flow offluids between the various openings. Such solenoid control valves arequite common in industrial use and will not be elaborated on furtherhere. Suffice it to say that the action of the solenoid valve will besufficient to achieve the desired communication between the variousopenings as appropriate to the performance of the sampler's function.

In actual practice, at the start of a sampling operation the internalconfiguration of the sampler will be similar to that shown in FIG. 4,with the sample collecting piston 120 at the top of its stroke, to thefar left in a non-limiting configuration as shown in FIG. 4, andpositioned to start collecting a sample. As indicated above, for thesampling step to start some external or predetermined signal will open apassage between the space where a sample is to collect to the left ofthe sampling piston 120, and the fluid to be sampled present in thespace surrounding the sampler. Even though that passage has been opened,sampling cannot commence unless the working fluid in space 130positioned behind and to the right of the sampling piston is displaced,thus allowing the sampling piston 120 to move from left to right aspresented in FIG. 4, thus allowing a volume to open to the left of thesampling piston into which a sample can collect.

At the start the solenoid valve will be positioned such that workingfluid in space 130 will enter passage 460 to flow through passage 410and enter the solenoid valve opening 408 from where it will beredirected to opening 430 and thence through passage 432 which is theintake to the hydraulic pump 450. In turn the hydraulic pump willpressure up the working fluid and discharge it through the dischargeport 418 to the solenoid valve opening 416, through the valve and outopening 412 and passage 414 into via the passages 141 and into the space170 where the bulk of the low pressure working fluid resides. Thisprocess can be continuous in transiting the working fluid from space 130to space 170 until the entire sample collection step has been completed.

Once sample collection is complete using any of the criteria describedin greater detail above, sample recovery in a representative conditioncan be initiated. For the sample to be considered representative, thesample pressure must be maintained at least, and preferably much higherthan the pressure at which the sample was collected. This requirement ismost easily met in this particular embodiment by activating the solenoidvalve to appropriately reconfigure its internal passageways.Essentially, by adjusting the internal settings of the solenoid valve,the inlet to the pump 432 is now in communication with the port 414,while the high pressure outlet of the pump 416, now communicates via 410to the space 130 where the high pressure working fluid pressurized bythe pump serves to maintain the sample in a representative state.

It should as well be obvious that this approach also provides a meansfor recovering a more representative sample during the actual samplingstep. Thus, during the actual collection step it is feasible to firstset the solenoid valve in such a configuration that sample will enterthe sampling space in front of the sampling piston. However, after asmall volume of sample has been collected, say 5 to 20 cc, the solenoidvalve can be switched so that the pump pushes pressurized working fluidback into space 130, thus increasing the pressure of the working fluidon the high pressure side to above the reservoir pressure, driving thecollected sample back into a single phase condition. By once againreversing the solenoid valve, additional sample can be collected andthen re-pressurized. This cycle of incremental sample collection andre-pressurization can be repeated a number of times until the desiredtotal volume of representative sample is collected. This is asignificant distinguishing feature of this design as no other existingdesign for sample collection can deliver such a representative sample.

The principal advantage of such an embodiment is the considerablyimproved simplicity of the overall design, because the need for acomplex metering section presented as item 160 in FIG. 2 as also in alllikelihood the need for the unidirectional check-valve 161 alsopresented in FIG. 2 can be eliminated. As shown in FIG. 4, the movementof working fluid between the high pressure side 130 and the low pressureside 170 will be controlled by the setting and the internal check valvesassociated with the solenoid valve.

The hydraulic pump exploited in the aforementioned embodiments is arelatively simple and conventional hydraulic pump with no exceptionalcapabilities. However, another non-limiting embodiment is presented inFIG. 5 which exploits a more complex pump design. This embodimentexploits a double acting hydraulic function available in certain uniquepump designs. Essentially, most simple hydraulic pumps have a specificand non-interchangeable intake and outlet port as shown in FIGS. 1 and4, such that irrespective of the direction of rotation of the motor, theintake and outlet ports remain fixed in their function. However, certainunique hydraulic pumps are available whereby simply reversing thedirection of rotation of the motor allows a reversal of the function ofthe two ports.

Turning to FIG. 5, consider for example the case where such a pump hasan inlet port marked as an example only as 551, and a correspondingoutlet port marked as 546, as shown in FIG. 5. Consider further thesituation where such a sampler has been positioned at a locationappropriate for collecting a sample. As discussed previously, before asample can be collected, working fluid, which is being held in place bythe dual acting check valves built into the body of the hydraulic pump,must be moved from the high pressure space 130 to the low pressure space170. If the electric motor were to be now rotated, and as an exampleonly, in say the clockwise direction, then, provided the internalconfiguration of pump and valves is appropriate, the port 546 connectedto the opening 560 will act as the inlet to the hydraulic pump, with theports identified as 551 serving to discharge working fluid as it goesthrough the pump into the low pressure side 170 of the working fluidspace. This process can be continuous in transiting the working fluidfrom space 130 to space 170 until the entire sample collection step hasbeen completed.

Once sample collection is complete using any of the criteria describedin greater detail above, sample recovery in a representative conditioncan be initiated. For the sample to be considered representative, thesample pressure must be maintained at least, and preferably much higherthan the pressure at which the sample was collected. This requirement ismost easily met in this particular embodiment by reversing the directionof the motor's rotation. When the motor's rotation is reversed, thecontrolled movement of a double acting hydraulic cylinder in conjunctionwith the dual action check valves will act to reverse the action of thepump. Essentially, by the simple expediency of reversing the motor'sdirection of rotation, the ports identified by the number 551 in FIG. 5now become the inputs to the pump, while the port 546 becomes the highpressure discharge port. It should be obvious that in this configurationthe pump can be used to move the working fluid from the low pressureside denoted by 170 in FIG. 5 to the high pressure side 130, and atsufficient pressure to maintain the sample in a representative stateduring recovery.

It should as well be obvious that this approach also provides a meansfor recovering a more representative sample during the actual samplingstep. Thus, during the actual collection step it is feasible to firstturn the motor in such a direction that sample will enter the samplingspace in front of the sampling piston. However, after a small volume ofsample has been collected, say 5 to 20 cc, the direction of the pump canbe reversed so that the pressure of the working fluid on the highpressure side increases above the reservoir pressure, driving thecollected sample back into a single phase condition. By once againreversing the motor's direction, additional sample can be collected andthen again re-pressurized. This cycle of incremental sample collectionand re-pressurization can be repeated a number of times until thedesired total volume of representative sample is collected.

In order to maximize the opportunities for such a sampling device acrossthe full range of potential reservoirs it might encounter, it isexpected that it will have a pressure rating of up to say 40,000 psi,though more likely this pressure rating will be in the 20,000 psi range.This pressure rating implies that the sampler can be immersed in anenvironment where the surrounding fluids are at a pressure of up to20,000 psi or 40,000 psi without the sampler suffering any mechanicalfailure.

The physical dimensions of the sampler may vary significantly dependingon the particular application, especially as dictated by the means ofconveyance to a reservoir of interest. In those instances where acarrier is in use for conveying the samplers, the diameter of thesampler might vary anywhere from one inch to as much as three inches ormore. However, for slickline or wireline applications the dimensions ofthe surface lubricator which is to be used to introduce the sampler intothe well bore, as also the internal diameter of the elements of the toolstring the sampler will need to traverse, tends to be the limitingfactor. In such cases the diameter will tend to be more in the range of2 inches with an overall length of 17 feet. However, it needs to be keptin mind that these dimensions are merely suggestions dictated byspecific operations and could vary significantly as the opportunity andthe means for conveyance change.

The power required to run the motor, the electronics, and the ancillarykit associated with the sampling step will also be a significantconsideration in the dimensions and performance of the sampler. Thus, ina slickline application the power will need to be provided by batterycells appropriately designed and sized for this application. However,these battery components are commercially readily available and do notneed to be elaborated on here. In a wireline or e-line application allthe power needed for the operation of the sampler will be delivered bythe electrical cable itself, resulting in a much simpler and shortersampler with an extended functional life downhole. In carrier basedoperations, the battery pack could be incorporated with the sampleritself or could be a larger and separate battery pack designed toaccommodate a larger number of samplers for extended working lifedownhole.

It should be obvious to one skilled in the art and enlightened by theteachings of this disclosure that the sample size collected can bevaried significantly and be influenced by the needs of a particularapplication or situation. The unique features of the disclosed designattending the present invention results in the elimination of asignificant amount of overall sampler volume and length in comparison tothe prior art. This eliminated volume and length can be exploited in thepresent design to deliver a much larger volume of captured sample.However, in the cause of flexibility and redundancy it might proveadvantageous to collect multiple samples rather than a single largesample. This is facilitated in the present design such that two or eventhree separate and distinct samplers might be run in the same overalldimensions as would deliver only a single sample volume in the moretraditional designs covered by the prior art. Accordingly, the samplevolume can range anywhere from 5 cc to in excess of 10,000 cc dependingon a particular application, without departing from the spirit of thisinvention.

While this invention has been described with reference to numerousembodiments, this description is not intended to be construed in alimiting sense. Instead it is expected that the discussed embodimentswould serve to demonstrate the versatile ability of the proposed samplerdesign to accommodate the capture and representative preservation ofsingle and complex multiphase streams of variable ratios and flow ratesof the various components that can be encountered during a well testoperation. Understandably, various modifications and combinations of theillustrative embodiments as well as other embodiments of the inventionwill be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled) 11.(canceled)
 12. (canceled)
 13. (canceled)
 14. (canceled)
 15. (canceled)16. (canceled)
 17. (canceled)
 18. (canceled)
 19. (canceled) 20.(canceled)
 21. A system for sampling a subterranean reservoir fluid, thesystem comprising: (a) a subterranean reservoir fluid inlet port; (b) atubular portion; (c) a piston sealably and movably disposed within thetubular portion, wherein the area in front of the piston and thesubterranean reservoir fluid inlet port define a sample gatheringchamber and further wherein the volume of the sample gathering chamberis expandable by lateral movement of the piston during collection of thesubterranean reservoir fluid and lateral movement of the piston isreversible for compressing the collected subterranean reservoir fluid;(d) a space for a working fluid defined by the back of the piston andone or more surfaces of the tubular portion; (e) a metering sectionencased within the tubular portion and having a restrictive passage forregulating the movement of the working fluid; (f) a motor mechanicallycoupled to a hydraulic pump, wherein the motor and hydraulic pump areincorporated within the tubular portion and are positioned such that theworking fluid may be pressurized after collection of the subterraneanreservoir fluid and further wherein the motor is capable of beingrotated in one direction during collection of the subterranean reservoirfluid and the opposite direction during compression of the collectedsubterranean reservoir fluid; (g) a power source for running the motor;and (h) an electronic controller for controlling the movement of themotor in order to maintain pressure within the system.
 22. The system ofclaim 21, further comprising a trigger for controlling collection of thesubterranean reservoir fluid within the sample gathering chamber throughthe subterranean reservoir fluid inlet port.
 23. The system of claim 21,further comprising a pressure monitoring device.
 24. The system of claim21, wherein the power source is a battery pack.
 25. The system of claim24, wherein the battery pack is rechargeable or containsnon-rechargeable cells.
 26. The system of claim 21 wherein theelectronic controller is pre-programmable.
 27. The system of claim 21,further comprising a gearbox for magnifying the torque generated by themotor.
 28. (canceled)
 29. (canceled)
 30. (canceled)
 31. (canceled) 32.(canceled)
 33. (canceled)
 34. (canceled)
 35. (canceled)
 36. (canceled)37. (canceled)
 38. (canceled)
 39. A sampling apparatus for sampling asubterranean reservoir fluid, the sampling apparatus comprising: (a) asubterranean reservoir fluid inlet port; (b) a tubular portion; (c) apiston sealably and movably disposed within the tubular portion, whereinthe area in front of the piston, the tubular portion and thesubterranean reservoir fluid inlet port define a sample gatheringchamber; (d) a space on the side of the piston opposite the fluid inletport for a working fluid; (e) a motor mechanically coupled to ahydraulic pump and positioned within the tubular portion such that theworking fluid may be pressurized; (f) a power source within the tubularportion for running the motor; and (g) an electronic controller forcontrolling the movement of the motor in order to maintain pressurewithin the system.
 40. A system for sampling a subterranean reservoirfluid, the system comprising: (a) an inlet port for collecting samplesof the subterranean reservoir fluid within a sample gathering chamber;(b) a tubular portion; (c) a piston sealably and movably disposed withinthe tubular portion, wherein the area in front of the piston and thesubterranean reservoir fluid inlet port defines the sample gatheringchamber and further wherein the volume of the sample gathering chamberis expandable by lateral movement of the piston during collection of thesubterranean reservoir fluid and further wherein lateral movement of thepiston is reversible for compressing the collected subterraneanreservoir fluid; (d) a motor mechanically coupled to a hydraulic pumpand capable of repeatedly pressurizing samples of the subterraneanreservoir fluid while being collected within the sample gatheringchamber above the pressure at which the samples are collected, whereinthe motor and hydraulic pump are within the tubular portion; and (e) apower source within the tubular portion for running the motor.
 41. Thesampling apparatus of claim 39, wherein the power source is a batterypack.
 42. The sampling apparatus of claim 41, wherein the battery packis rechargeable or contains non-rechargeable cells.
 43. The samplingapparatus of claim 39, wherein the power source is an electrical cable.44. The sampling apparatus of claim 40, further comprising a set ofgears within the tubular portion for the motor mechanically coupled tothe hydraulic pump.
 45. The system of claim 24, wherein each of thehydraulic pump, the motor and the battery pack have passages for entryof the working fluid.
 46. A sampling apparatus for sampling asubterranean reservoir fluid wellbore, the sampling apparatuscomprising: (a) a fluid inlet port and a tubular portion; (b) a pistonsealably and movably disposed within the tubular portion, wherein one ormore surfaces of the piston and the tubular portion in conjunction withthe fluid inlet port define a sample gathering chamber; (c) a space fora working fluid opposite the side of the piston defining the samplegathering chamber; (d) a pump positioned within the tubular portion suchthat fluid intake into the pump is located on the low pressure side ofthe working fluid space; (e) a motor mechanically positioned within thetubular portion and coupled to the pump; (f) an electronic controllerfor activating the motor and pump by the differential pressure on theworking fluid space; and (g) a power source positioned within thetubular portion for running the motor.
 47. The sampling apparatus ofclaim 46, further comprising a pressure monitoring device.
 48. Thesampling apparatus of claim 46, further comprising a gearbox formagnifying torque generated by the motor.
 49. The sampling apparatus ofclaim 46, wherein the power source is a battery pack.
 50. The samplingapparatus of claim 49, wherein the battery pack is rechargeable orcontains non-rechargeable cells.
 51. The sampling apparatus of claim 46,further comprising an electronic controller capable of controlling themovement of the motor in order to maintain pressure within the tubularportion.